Air blast circuit breakers



Sept. 15, 1959 FQRWALD I 2,904,660

AIR BLAST CIRCUIT BREAKERS Filed March ll, 1958 a l||l INVENTOR. HaakonEarn/a Zd United States Patent AIR BLAST CIRCUIT BREAKERS HaakonForwald, Ludvika, Sweden, assignor to, Allmiinna Svenska ElektriskaAktieboiaget, Vasteras, Sweden, a corporation of Sweden ApplicationMarch 11, 1958, Serial No. 720,727

Claims priority, application Sweden March 15, 1957 3 Claims. (Cl.200-148) Sometimes a persisting breaking arc can occur in compressed aircircuit breakers. This happens if the breaker is exposed toshort-circuiting effects higher than the effect it was rated for. Such apersisting arc causes more or less serious damage to the elements insidethe circuit breaker due to the heat produced by the arc. Even if therisk of explosions can be avoided by arranging a safety membrane, apersisting are always means a serious drawback because the breaker isconsiderably damaged, and the present invention relates to anarrangement for avoiding such damage. The invention is mainlycharacterized in that the breaker is provided with a member which, atthe occurrence of such a pressure as that produced by the persistingarc, immediately closes the breaker and leaves it to other breakerspresent in the network to take care of the interruption of theshortcircuiting eifect. The invention is further characterized by thefact that this member opens the operating circuit performing the openingof the breaker, so that there is no risk of the breaker being openedagain before the fault has been eliminated and the damaged parts havebeen replaced.

On the accompanying drawing, Fig. 1 shows schematically a circuitbreaker with an arrangement according to the invention for preventingthe formation of a persisting arc, and Fig. 2 shows in detail the designof members performing the recoupling of the breaking gap at theoccurrence of breaking arcs. On the drawing, 1 designates a compressedair container to which a pillar insulator 2 is attached carrying afurther compressed air container 3, in which a leading through insulator4 and an operating member 5 are located. The insulator 4 carries thestationary contact and the operating member 5 carries the movablecontact in the breaking gap. The movable contact is operated by aid ofcompressed air which is supplied through a pipe line 6. This pipe lineis connected with a valve 7, which is joined with the compressed aircontainer 1, and the valve 7 is operated by both magnet coils 8 and 9,which are supplied with current over the contacts 10, 11, respectively.The coil 8 serves for closing the breaker while the coil 9 serves foropening the breaker. The contacts 10 and 11, in their turn, are operatedby a member 12 attached in the compressed air container 1. Besides thereare buttons 13 and "ice 14 for manually closing and opening the circuitbreaker. The pressure sensitive member 12 consists of a cylinder 15, inwhich a piston v16 is movably arranged, which is actuated by a spring 17counteracting the air pressure. The piston 16 is provided with a rod 18,which acts on a catch 19, which in its turn acts on a rod 20, which,under the influence of a spring 21, tends to move downwards when thecatch 19 does not engage the hook on the rod 20. The rod 20 is arrangedto engage at its movement the contacts 10 and 11, respectively, by beingprovided with contact bridges 22 and 23 which close the contacts 10 and11, respectively.

The arrangement acts in such a way that, if due to a persisting arebetween the main contacts in the compressed air container 3, a heatingshould take place so that the pressure in the container will exceed acertain value, the piston 16 is moved to the right. Then the rod 18pushes the catch 19 sideways, so that the rod 20 is released and moveddownwards by the spring 21, so that the contact bridges attached to therod close the closing contacts 10 and open the opening contacts 11. Thissafety device consisting of the cylinder 15 with the piston 16, thecatch 19 and contact rod 20 is normally arranged in such a way that itcan only be put back into its original position manually, but of coursenothing prevents if from being moved back automatically, but this can ofcourse only be performed when the circuit breaker has been inspected andhas proved to be quite all right.

I claim as my invention:

1. Arrangement in an air blast circuit breaker for preventing persistingarcs between the breaking contacts, comprising a compressed aircontainer, operating members for the circuit breaker, and a pressuresensitive member so connected with the said container that an increasein pressure within the said container due to the heat generated by thearc causes the said sensitive member to so actuate the said operatingmembers that the circuit breaker is closed.

2. Arrangement according to claim 1, characterized in that the pressuresensitive member is a cylinder which is connected to the compressed aircontainer and contains a piston actuated by a spring, which piston underthe influence of a certain increase of pressure, actuates the operatingmembers of the circuit breaker in closing direction and blocks itsmembers in opening direction.

3. Arrangement according to claim 2, characterized in that the piston atits movement actuates a catch in such a manner that this releases a rodactuated by a spring, which rod carried two contact bridges, one ofthese being arranged to close the current circuit for closing thebreaker and the other one for interrupting the operating members of thecircuit breaker for its opening.

References Cited in the file of this patent FOREIGN PATENTS 477,693Germany June 12, 1929

